Good point there Northwind.
The thing with Enduro (unlike say XC where there is a pretty standard skinny whippet roadie build!), is the range of physiques competing. You could have an XC rider who has polished up their technical skills being pretty good, or a DH racer who has worked on fitness, or a trail rider getting into racing after years of being just out on the trails.
Each will have very different muscle development from their different riding styles and from a varied physiological start point (ectomorph, endomorph or mesomorph).
Some will be good at “sit & spin” climbing, some will be hulking beasts like Mark Weir who can pull a 38t single ring.
It’s a varied thing and so by definition there’s no hard & fast rule. Take a good hard honest look at how you ride, how often you use the granny, what cadences you can push, how your knees feel at the end of a big ride etc etc.
Oh and if you go 2×10 the C-Guide is great.
Hope my amazing “catch all” and probably quite confusing non-answer helps…….. :-/